The present invention relates to a novel nitrogen-containing heterocyclic compound, an organic light-emitting device material comprising such a nitrogen-containing heterocyclic compound and an organic light-emitting device containing such a nitrogen-containing heterocyclic compound.
Today, various display devices comprising organic fluorescent materials are under extensive study. Among these display devices, organic EL (electroluminescence) devices can emit light having a high luminance even when driven at a low voltage and thus are noted as favorable display device. For example, an EL device comprising an organic thin film layer formed by evaporation of an organic compound has been known (as disclosed in Applied Physics Letters, vol. 51, page 913, 1987). The organic EL device disclosed in the above cited reference has a laminated structure comprising an electron-transporting material and a positive hole-transporting material and thus exhibits drastically improved light-emitting properties as compared with the conventional single-layer devices.
With this report as a turning-point, organic EL devices have been under extensive research and development. Accordingly, the development of electron-transporting materials and hole-transporting materials providing an enhanced light-emitting efficiency have been extensively studied. However, no compounds superior to Alq(Tris(8-hydroxyquinolinato)aluminum) have been found yet in the development of electron-transporting materials. It has thus been desired to provide improved electron-transporting materials. Further, Alq fluoresces green and thus is not appropriate as an electron-transporting material for blue light-emitting device. This, too, is why the development of improved electron-transporting materials has been desired.
Moreover, the application of organic EL devices to full-color display has been recently studied extensively. In order to develop a high performance full-color display, it is necessary to enhance the purity of the colors, i.e., blue, green and red, of light emitted. However, it is difficult to emit light having a high color purity. For example, benzo-condensed nitrogen-containing heterocyclic compounds as disclosed in Seizo Miyata, Organic EL devices and its forefront of industrialization, NTS, page 40, 1998, JP-A-7-133483 (The term xe2x80x9cJP-Axe2x80x9d as used herein means an xe2x80x9cunexamined published Japanese patent applicationxe2x80x9d), and JP-A-10-330744 are widely studied blue light-emitting materials but can emit only a blue light having a low color purity. It has thus been desired to provide organic EL devices having an improved color purity.
It is therefore an object of the present invention to provide an organic light-emitting device material such as electron-transporting material and light-emitting material capable of emitting light having a high luminance and a high color purity.
The foregoing object of the present invention will become apparent from the following detailed description and examples.
The foregoing object of the present invention is accomplished by the following aspects of the present invention:
(1) An organic light-emitting device material comprising a compound having a partial structure represented by the following general formula (I): 
wherein R11 and R12 each represent a hydrogen atom or a substituent, with the proviso that R11 and R12 are not bonded to form a benzo condensed ring; X1 represents an oxygen atom, a sulfur atom, a substituted or unsubstituted nitrogen atom or xe2x80x94C(R13)R14xe2x80x94; R13 and R14 each represent a hydrogen atom or a substituent; Y1 represents an oxygen atom, a sulfur atom or a substituted or unsubstituted nitrogen atom; M1 represents a metal ion or a hydrogen atom; and Z1 represents an atomic group required to form a 5- or 6-membered ring.
(2) An organic light-emitting device material comprising a compound having a partial structure represented by the following general formula (II): 
wherein Q1 represents an atomic group required to form a heterocyclic group; X2 represents an oxygen atom, a sulfur atom, a substituted or unsubstituted nitrogen atom or xe2x80x94C(R15)R16xe2x80x94; R15 and R16 each represent a hydrogen atom or a substituent; Y2 represents an oxygen atom, a sulfur atom or a substituted or unsubstituted nitrogen atom; M2 represents a metal ion or a hydrogen atom; and Z2 represents an atomic group required to form a 5- or 6-membered ring.
(3) A compound represented by the following general formula (III): 
wherein R21 and R22 each represent a hydrogen atom, an alkyl group, an aryl group or a heteroaryl group; X3 represents an oxygen atom, a sulfur atom, a substituted or unsubstituted nitrogen atom or xe2x80x94C(R23)R24xe2x80x94; R23 and R24 each represent a hydrogen atom or a substituent; Y3 represents an oxygen atom, a sulfur atom or a substituted or unsubstituted nitrogen atom; M3 represents a metal ion; q1 represents an integer of not less than 1; L1 represents a ligand; me represents an integer of not less than 0; and Z3 represents an atomic group required to form a 5- or 6-membered ring.
(4) A compound represented by the following general formula (IV): 
wherein Q2 represents an atomic group required to form a heterocyclic group; X3 represents an oxygen atom, a sulfur atom, a substituted or unsubstituted nitrogen atom or xe2x80x94C(R25)R26xe2x80x94; R25 and R26 each represent a hydrogen atom or a substituent; Y4 represents an oxygen atom, a sulfur atom or a substituted or unsubstituted nitrogen atom; M4 represents a metal ion; q2 represents an integer of not less than 1; L2 represents a ligand; m2 represents an integer of not less than 0; and Z4 represents an atomic group required to form a 5- or 6-membered ring.
(5) An organic light-emitting device comprising a pair of electrodes having a light-emitting layer or a plurality of organic thin film layers containing said light-emitting layer formed interposed therebetween, wherein at least one of said plurality of organic thin film layers comprises at least one of compounds defined in the foregoing aspects (1) to (4) of the present invention incorporated therein.
(6) The organic light-emitting device according to the aspect (5), wherein at least one of said plurality of organic thin film layers is formed by a coating process.
The foregoing compound of the present invention is a compound having a partial structure represented by the general formula (I). The compound having a partial structure represented by the general formula (I) is preferably a metallic complex. Such a metallic complex may be a compound having at least one partial structure represented by the general formula (I) incorporated therein. The metallic complex may also be a so-called polynuclear complex having a plurality of metal specifies per molecule. Further, the metallic complex may have a plurality of ligands. More preferably, the compound of the present invention is a neutral metallic complex. 
The general formula (I) will be further described hereinafter.
R11 and R12 each represent a hydrogen atom or a substituent. Examples of the substituent represented by R11 or R12 include an alkyl group (preferably C1-20 (wherein xe2x80x9cC1-20xe2x80x9d, means 1 to 20 carbon atoms, hereinafter the same), more preferably C1-12, particularly C1-8 alkyl group such as methyl, ethyl, iso-propyl, tert-butyl, n-octyl, n-decyl, n-hexadecyl, cyclopropyl, cyclopentyl and cyclohexyl), an alkenyl group (preferably C2-20, more preferably C2-12, particularly C2-8 alkenyl group such as vinyl, allyl, 2-butenyl and 3-pentenyl), an alkinyl group (preferably C2-20, more preferably C2-12, particularly C2-8 alkinyl group such as propargyl and 3-pentinyl), an aryl group (preferably C6-30, more preferably C6-20, particularly C6-12 aryl group such as phenyl, p-methylphenyl and naphthyl), a substituted carbonyl group (preferably C1-20, more preferably C1-16, particularly C1-12 substituted carbonyl group such as acetyl, benzoyl, methoxycarbonyl, phenyloxycarbonyl, dimethylaminocarbonyl and phenylaminocarbonyl), an amino group (preferably C0-20, more preferably C1-16, particularly C1-12 amino group such as dimethylamino, methylcarbonylamino, ethylsulfonylamino, dimethylaminocarbonylamino and phthalimide), a sulfonyl group (preferably C1-20, more preferably C1-16, particularly C1-12 sulfonyl group such as mesyl and tosyl), a sulfo group, a carboxyl group, a heterocyclic group (e.g., aliphatic heterocyclic group, aromatic heterocyclic group, preferably C1-50 so more preferably C1-30, particularly C2-12 heterocyclic group preferably containing any of oxygen atom, sulfur atom and nitrogen atom such as imidazolyl, pyridyl, furyl, piperidyl, morpholino, benzoxazolyl and triazolyl), a hydroxyl group, an alkoxyl group (preferably C1-20, more preferably C1-16, particularly C1-12 alkoxyl group such as methoxy and benzyloxy), an aryloxy group (preferably C6-20, more preferably C6-16 particularly C6-12 aryloxy group such as phenoxy and naphthyloxy), a halogen atom (preferably fluorine, chlorine, bromine, iodine), a thiol group, an alkylthio group (preferably C1-20, more preferably C1-16, particularly C1-12 alkylthio group such as methylthio), an arylthio group (preferably C6-20, more preferably C6-16, particularly C6-12 arylthio group such as phenylthio), a cyano group, and a silyl group (preferably C0-40, more preferably C3-30, particularly C3-18 silyl group such as trimethylsilyl, triphenylsilyl and t-butyldiphenylsilyl). These substituents may be further substituted.
R11 and R12 may be connected to each other to form a ring (such as a heterocyclic group (preferably C2-20, more preferably C3-12, particularly C3-8 heterocyclic group containing as hetero atom nitrogen atom, oxygen atom, sulfur atom or selenium atom, such as heterocyclic group represented by Q1 shown later) and particularly C2-8 alkinyl group such as propargyl and 3-pentinyl), an aryl group (preferably C6-30, more preferably C6-20, particularly C6-12 aryl group such as phenyl, p-methylphenyl and naphthyl), a substituted carbonyl group (preferably C1-40, more preferably C1-20, particularly C1-12 substituted carbonyl group such as acetyl, benzoyl, methoxycarbonyl, dimethylaminocarbonyl and phenylamino carbonyl), a substituted sulfonyl group (preferably C1-20, more preferably C1-16, particularly C1-12 substituted sulfonyl group such as mesyl and tosyl), and a heterocyclic group (preferably C1-20, more preferably C1-16 particularly C1-12 heterocyclic group preferably having any of oxygen atom, sulfur atom and nitrogen atom, such as imidazolyl, pyridyl, furyl and piperidyl). These substituents may be further substituted. Preferred among these substituents on nitrogen are an alkyl group, an aryl group and an aromatic heterocyclic group. Particularly preferred among these substituents are an alkyl group and an aryl group.
R13 and R14 each preferably are a hydrogen atom, an alkyl group or an aryl group, more preferably a hydrogen atom or an alkyl group, particularly an alkyl group.
X1 is preferably an oxygen atom, a sulfur atom or a substituted or unsubstituted nitrogen atom, more preferably an oxygen atom or a substituted nitrogen atom, even more preferably an oxygen atom, an alkyl group-substituted nitrogen atom or an aryl group-substituted nitrogen atom, particularly preferably an aryl group-substituted nitrogen atom.
Y1 represents an oxygen atom, a sulfur atom or a a cycloalkene ring (preferably C4-20, more preferably C5-12, particularly C5-8 cycloalkene ring such as cyclohexene ring and cyclopentene ring)). However, R11 and R12 are not connected to each other to form a benzo condensed ring (including benzene ring, naphthalene ring and anthracene ring).
R11 and R12 each preferably are a hydrogen atom, an alkyl group, an aryl group, an aromatic heterocyclic group or one of groups which are connected to each other to form a heterocyclic group, more preferably a hydrogen atom, an alkyl group, an aryl group or one of groups which are connected to each other to form a heterocyclic group, particularly a hydrogen atom, an aryl group or one of groups which are connected to each other to form a heterocyclic group.
X1 represents an oxygen atom, a sulfur atom, a substituted or unsubstituted nitrogen atom or xe2x80x94CR13(R14)xe2x80x94.
The term xe2x80x9cunsubstituted nitrogen atomxe2x80x9d as used herein is meant to indicate xe2x80x94NHxe2x80x94.
R13 and R14 each represent a hydrogen atom or a substituent. Examples of such a substituent include those described with reference to R11. Examples of the substituent on nitrogen include an alkyl group (preferably C1-20, more preferably C1-12, particularly C1-8 alkyl group such as methyl, ethyl, iso-propyl, tert-butyl, n-octyl, n-decyl, n-hexadecyl, cyclopropyl, cyclopentyl and cyclohexyl), an alkenyl group (preferably C2-20, more preferably C2-12, particularly C2-8 alkenyl group such as vinyl, allyl, 2-butenyl and 3-pentenyl), an alkinyl group (preferably C2-20, more preferably C2-12, substituted or unsubstituted nitrogen atom. Examples of the substituent on nitrogen include those described with reference to X1. Preferred among these substituents are a substituted sulfonyl group and a substituted carbonyl group. More desirable among these substituents is a substituted sulfonyl group. Even more desirable among these substituents is an arylsulfonyl group.
Preferred among the groups represented by Y1 are an oxygen atom and a substituted nitrogen atom. Even more desirable among these groups is an oxygen atom.
Z1 represents an atomic group required to form a 5- or 6-membered ring. The ring containing Z1 may have substituents (Examples of these substituents include those described with reference to substituent on R11) or may be condensed to other rings.
Examples of the ring containing Z1 include cyclopentene, cyclohexene, benzene, naphthalene, anthracene, phenanthrene, pyrene, perylene, pyridine, quinoline, furan, thiophene, pyrazine, pyrimidine, thiazole, benzothiazole, naphthothiazole, oxazole, benzoxaole, naphthoxazole, isoxazole, selenazole, benzoselenazole, naphthoselenazole, imidazole, benzoimidazole, naphthoimidazole, isoquinoline, pyrazole, and triazole.
The ring containing Z1 is preferably an aromatic ring. Preferred examples of such an aromatic ring include benzene, naphthalene, anthracene, pyridine, thiophene, pyrazine, and pyrimidine. More desirable among these aromatic rings are benzene and naphthalene. Even more desirable among these aromatic rings is benzene.
M1 represents a metal ion or a hydrogen atom. M1 is preferably a metal ion. The metal ion represented by M1 is not specifically limited but is preferably a divalent or trivalent metal ion, more preferably Be2+, Mg2+, Al3+ or Zn2+, even more preferably Al3+ or Zn2+.
A preferred embodiment of the partial structure represented by the general formula (I) is the following general formula (II): 
The general formula (II) will be further described hereinafter. Q1 represents a group required to form a heterocyclic group (e.g., aliphatic heterocyclic group, aromatic heterocyclic group, preferably C2-20, more preferably C3-15, particularly C4-10 heterocyclic group preferably containing any of oxygen atom, sulfur atom and nitrogen atom, such as pyridine ring, pyrazine ring, pyrimidine ring, quinoline ring, indole ring, furan ring, pyran ring, pyrrole ring, imidazole ring, pyrazole ring, thiophene ring, dihydropyran ring and dihydropyridine). Q1 may have a substituent thereon. Examples of the substituent on Q1 include those described with reference to R11. Preferred among the heterocyclic groups formed by Q1 are pyridine ring, pyrazine ring, and pyrimidine ring. More desirable among these heterocyclic groups are pyridine ring and pyrazine ring. Even more desirable among these heterocyclic groups is pyridine ring.
X2, Z2, Y2 and M2 in the general formula (II) have the same meaning and preferred range as X1, Z1, Y1 and M1 in the general formula (I).
The number of metal ions in the metallic complex having a partial structure represented by the general formula may be one or plural. The number of the kinds of metal ions may be one or plural. The metallic complex is preferably one containing two or less metal ions of two or less kinds, more preferably two or less metal ion of one kind, even more preferably one metal ion of one kind.
The number of the kinds of ligands in the metallic complex having a partial structure represented by the general formula (I) may be one or plural. The number of the kinds of ligands in the metallic complex is preferably from 1 to 3, more preferably 1 or 2, and further more preferably 1 (only one ligand derived from the partial structure represented by the general formula (I)). An example of ligands other than the ligand derived from the partial structure represented by the general formula (I) is L1 shown below.
The metallic complex having a partial structure represented by the general formula (I) preferably fluoresces at a maximum wavelength (xcexmax) of from not less than 370 nm to not more than 490 nm, more preferably from not less than 390 nm to not more than 470 nm, even more preferably from not less than 390 nm to not more than 450 nm.
The compound of the present invention (preferably compound having a partial structure represented by the general formula (I), preferably compound having a partial structure represented by the general formula (II)) is preferably a metallic complex represented by the general formula (III)(more preferably a metallic complex represented by the general formula (IV)), more preferably a metallic complex represented by the general formula (V)(preferably a metallic complex represented by the general formula (VI)), even more preferably a metallic complex represented by the general formula (VII) (preferably a metallic complex represented by the general formula (VIII)), particularly a metallic complex represented by the general formula (IX) or (X). 
The general formula (III) will be further described hereinafter.
Z3, X3 and Y3 have the same meaning and preferred range as Z1, X1 and Y1, respectively. R21 and R22 each represent a hydrogen atom, an alkyl group, an aryl group or a heteroaryl group, preferably an alkyl group or an aryl group, more preferably an aryl group. M3 represents a metal ion. The metal ion represented by M3 has the same examples and preferred range as the metal ion represented by M1.
L1 represents a unidentate or multidentate ligand. Examples of such a ligand include a halogen ion (e.g., Clxe2x88x92, Brxe2x88x92, Ixe2x88x92), a perchlorate ion, an alkoxy ion (preferably C1-20, more preferably C1-10, even more preferably C1-5 alkoxy ion such as methoxy ion, ethoxy ion, isopropoxy ion and acetylacetone ion), an aryloxy ion (preferably C6-20, more preferably C6-12, even more preferably C6-8 aryloxy ion such as phenoxy ion, quinolinol ion and 2-(2-hydroxyphenyl)benazole ion), a nitrogen-containing heterocyclic group (preferably, C1-20, more preferably C2-10, even more preferably C3-8 nitrogen-containing heterocyclic group such as phenanthrene and bipyridyl), an acyloxy ion (preferably C1-20 more preferably C2-10, even more preferably C3-8 acyloxy group such as acetyloxy ion), an ether compound (preferably C2-20, particularly C3-10, even more preferably C3-8 ether compound such as tetrahydrofuran), and a hydroxy ion. Preferred among these ligands are an alkoxy ion, and an aryloxy ion. Particularly preferred among these ligands is an aryloxy ion.
The suffix q1 represents an integer of not less than 1, and the suffix m1 represents an integer of not less than 0. The preferred range of q1 and m1 depend on the kind of metal ion and is not specifically limited. In practice, however, q1 is preferably from 1 to 4, more preferably from 1 to 3, particularly from 2 or 3, and m1 is preferably from 0 to 2, more preferably 0 or 1, particularly 0. The combination of q1 and m1 is preferably such that the metallic complex represented by the general formula (III) is a neutral complex.
The general formula (IV) will be further described hereinafter.
X4, Y4, Z4, Q2, M4, L2, q2 and m2 have the same meaning and preferred range as X2, Y2, Z2, Q1, M3, L1, q1 and m1, respectively.
The general formula (V) will be further described hereinafter.
R31, R32, Z5, X5, Y5 and M5 have the same meaning and preferred range as R21, R22, Z1, X1, Y1 and M3, respectively. The suffix q3 represents an integer of not less than 2, preferably 2, 3 or 4, more preferably 2 or 3.
The general formula (VI) will be further described hereinafter.
X6, Y6, Z6, Q3, M6 and q4 have the same meaning and preferred range as X2, Y2, Z2, Q1, M4 and q3, respectively.
The general formula (VII) will be further described hereinafter.
R41, R42, X7, Y7, M7 and q5 have the same meaning and preferred range as R21, R22, X1, Y1, M3 and q3 respectively. R45 represents a substituent. Examples of the substituent include those described with reference to substituent on R11. R45 is preferably an alkyl group, an alkenyl group, an aryl group, a heteroaryl group, an alkoxy group or a cyano group, more preferably an alkyl group or an aryl group, even more preferably an alkyl group. The suffix n1 represents an integer of from 0 to 4, preferably 0 or 1, more preferably 0.
The general formula (VIII) will be further described hereinafter.
X8, Y8, Q4, M8, q6, R46 and n2 have the same meaning and preferred range as X2, Y2, Q1, M3, q3, R45 and n1, respectively.
The general formula (IX) will be further described hereinafter. R51, R52, X9, M9, q7, R55 and n3 have the same meaning as R21, R22, X1, M7, q5, R45 and n1.
The general formula (X) will be further described hereinafter.
M10, q8, R56 and n4 have the same meaning and preferred range as M3, q3, R45 and n1, respectively. R57 represents a substituent. The substituent represented by R57 has the same examples and preferred range as R56. The suffix n5 represents an integer of from 0 to 3, preferably 0 or 1, more preferably 0. R58 represents a substituent. Examples of the substituent represented by R58 include those described with the substituent on nitrogen of X1. R58 is preferably an alkyl group, an aryl group or a heteroaryl group, more preferably an aryl group.
The compound of the present invention may be a polymer compound but is preferably a low molecular weight compound.
Examples of the compound of the present invention will be given below, but the present invention should not be construed as being limited thereto. 
The compound of the present invention can be prepared in accordance with a known synthesis method as disclosed in JP-A-10-330744.
The organic light-emitting device comprising a compound of the present invention will be further described hereinafter. The organic light-emitting device of the present invention is not limited in system, driving method, application, etc. so far as it utilizes the emission of light from the compound of the present invention. A representative example of the organic light-emitting device of the present invention is an organic EL (electroluminescence) device.
The present invention will be further described with reference to the organic EL device comprising a compound of the present invention.
As described in Applied Physics Letters, vol. 51, page 913, 1987, the organic EL device preferably comprises an organic layer having a laminated structure. The method for the preparation of the organic layer in the EL device comprising a compound of the present invention is not specifically limited. In practice, however, resistance heating metallizing method, electron beam method, sputtering method, molecular lamination method, coating method, ink jet method, etc. can be used. From the standpoint of properties and preparation, resistance heating metallizing method or coating method is preferred.
The light-emitting device of the present invention is a device comprising a pair of electrodes, i.e., anode and cathode, having a light-emitting layer or a plurality of organic thin film layers containing said light-emitting layer formed interposed therebetween. Besides the light-emitting layer, a positive hole-injecting layer, a positive hole-transporting layer, an electron-injecting layer, an electron-transporting layer, a protective layer, etc. may be incorporated in the light-emitting device of the present invention. These layers each may have additional functions. These layers each may be formed by various materials.
The anode supplies positive holes into the positive hole-injecting layer, positive hole-transporting layer, light-emitting layer, etc. The anode can be made of a metal, alloy, metal oxide, electrically-conductive compound or mixture thereof preferably, a material having a work function of not less than 4e is used. Specific examples of such a material include electrically-conductive metal oxide such as tin oxide, zinc oxide, indium oxide and indium tin oxide (ITO), metal such as gold, silver, chromium and nickel, mixture or laminate of such a metal and electrically-conductive metal oxide, inorganic electrically-conductive material such as copper iodide and copper sulfide, organic electrically-conductive material such as polyaniline, polythiophene and polypyrrole, and laminate of such an inorganic or organic electrically-conductive material with ITO. Preferred among these materials is electrically-conductive metal oxide. In particular, ITO is preferred from the standpoint of productivity, electrical conductivity, transparency, etc. The thickness of the anode may be properly predetermined depending on the kind of the anode material. In practice, however, it is preferably from 10 nm to 5 xcexcm, more preferably from 50 nm to 1 xcexcm, even more preferably from 100 nm to 500 nm.
The anode is normally formed as a layer on a soda lime glass, alkali-free glass, transparent resin substrate or the like. The glass, if used, is preferably alkali-free glass to minimize the amount of ions eluted therefrom. The soda lime glass, if used, is preferably provided with a barrier coat of silica or the like. The thickness of the substrate is not specifically limited so far as it is great enough to maintain the desired mechanical strength. If the substrate is glass, its thickness is normally not less than 0.2 mm, preferably not less than 0.7 mm.
The preparation of the anode can be accomplished by a proper method depending on the anode material used. For example, if the anode material is ITO, electron beam method, sputtering method, resistance heating metallizing method, chemical reaction method (e.g., sol-gel method), method involving the application of a dispersion of indium tin oxide, or the like may be employed. The anode thus prepared can be cleaned or otherwise treated to lower the driving voltage of the device or raise the light-emitting efficiency of the device. For example, if the anode material is ITO, UV-ozone treatment, plasma treatment or the like is effective.
The cathode supplies electron into the electron-injecting layer, electron-transporting layer, light-emitting layer, etc. The form of the cathode is predetermined according to the adhesivity of the cathode to the adjacent layer such as electron-injecting layer, electron-transporting layer and light-emitting layer, the ionization potential of the cathode, the stability of the cathode, etc. The cathode may be formed by a metal, alloy, metal halide, metal oxide, electrically-conductive compound or mixture thereof. Specific examples of such a material include alkaline metal (e.g., Li, Na, K), fluoride thereof, alkaline earth metal (e.g., Mg, Ca), fluoride thereof, gold, silver, lead, aluminum, sodium-potassium alloy, mixture thereof, lithium-aluminum alloy, mixture thereof, magnesium-silver alloy, mixture thereof, and rare earth metal such as indium and ytterbium. Preferred among these materials are those having a work function of not more than 4eV. More desirable among these materials are aluminum, lithium-aluminum alloy, mixture thereof, magnesium-silver alloy, and mixture thereof. The cathode may have either a single-layer structure made of the foregoing compounds or mixture thereof or a laminated structure containing the foregoing compounds or mixture thereof. The thickness of the cathode may be properly predetermined depending on the kind of the cathode material. In practice, however, it is preferably from 10 nm to 5 xcexcm, more preferably from 50 nm to 1 xcexcm, even more preferably from 100 nm to 1 xcexcm.
The preparation of the cathode can be accomplished by electron beam method, sputtering method, resistance heating metallizing method, coating method or the like. A single metal may be evaporated. Alternatively, two or more metals may be evaporated at the same time. Further, a plurality of metals mat be evaporated at the same time to form an alloy electrode. Alternatively, an alloy which has been previously prepared may be evaporated. The sheet resistivity of the anode and cathode is preferably as low as not greater than several hundreds of xcexa9/xe2x96xa1.
The light-emitting layer may be made of any material capable of forming a layer which acts to receive positive holes from the anode or positive hole-injecting layer or positive hole-transporting layer while receiving electron from the cathode or electron-injecting layer or electron-transporting layer under the application of electric field, allows the electric charge thus injected to move and provide a site for the recombination of positive hole and electron to emit light. Examples of such a material include compounds of the present invention, benzoxazole derivative, benzoimidazole derivative, benzothiazole derivative, styrylbenzene derivative, polyphenyl derivative, diphenylbutadiene derivative, tetraphenylbutadiene derivative, naphthalimide derivative, coumarin derivative, perylene derivative, perinone derivative, oxadiazole derivative, aldazine derivative, pyralidine derivative, cyclopentadiene derivative, bisstyrylanthracene derivative, quinacridone derivative, pyrrolopyridine derivative, thiadiazolopyridine derivative, cyclopentadiene derivative, styrylamine derivative, organic silicon derivative, organic boron derivative, aromatic dimethylidine compound, various metallic complexes such as metallic complex of 8-quinolinol derivative and rare earth complex, and polymer compound such as polythiophene, polyphenylene and polyphenylvinylene. The thickness of the light-emitting layer is not specifically limited. In practice, however, it is preferably from 1 nm to 5 xcexcm, more preferably from 5 nm to 1 xcexcm, even more preferably from 10 nm to 500 nm.
The method for the formation of the light-emitting layer is not specifically limited. In practice, however, resistance heating metallizing method, electron beam method, sputtering method, molecular lamination method, coating method (spin coating method, casting method, dip coating method, etc.), LB method, ink jet process or the like maybe used. Preferred among these methods are resistance heating metallizing method and coating method.
The positive hole-injecting layer and positive hole-transporting layer may be formed by any material capable of injecting positive holes from the anode, transporting positive holes or providing barrier against electron injected from the cathode. Specific examples of such a material include electrically-conductive high molecular weight oligomers such as carbazole derivative, triazole derivative, oxazole derivative, oxadiazole derivative, imidazole derivative, polyarylalkane derivative, pyrazoline derivative, pyrazolone derivative, phenylenediamine derivative, arylamine derivative, amino-substituted chalcone derivative, styrylanthracene derivative, fluorenone derivative, hydrazone derivative, stilbene derivative, silazane derivative, aromatic tertiary amine compound, styrylamine compound, aromatic dimethylidene compound, porphiline compound, polysilane compound, poly(N-vinylcarbazole) derivative, aniline copolymer, thiophene oligomer and polythiophene. The thickness of the positive hole-injecting layer and positive hole-transporting layer is not specifically limited. In practice, however, it is preferably from 1 nm to 5 xcexcm, more preferably from 5 nm to 1 xcexcm, particularly preferably from 10 nm to 500 nm. The positive hole-injecting layer and positive hole-transporting layer may have either a single-layer structure comprising one or more of the foregoing materials or a multi-layer structure comprising a plurality of layers having the same or different compositions.
The formation of the positive hole-injecting layer and positive hole-transporting layer can be accomplished by vacuum evaporation method, ink jet method, LB method, or method involving the application of a solution or dispersion of the foregoing positive hole-injecting and transporting materials in a solvent (spin coating method, casting method, dip coating method, etc.). If coating method is used, these positive hole-injecting and transporting materials may be dissolved or dispersed with a resin component. Examples of such a resin component include polyvinyl chloride, polycarbonate, polystyrene, polymethyl methacrylate, polybutyl methacrylate, polyester, polysulfone, polyphenylene oxide, polybutadiene, poly(N-vinylcarbazole), hydrocarbon resin, ketone resin, phenoxy resin, polyamide, ethyl cellulose, vinyl acetate, ABS resin, polyurethane, melamine resin, unsaturated polyester resin, alkyd resin, epoxy resin, and silicone resin.
The electron-injecting layer and electron-transporting layer may be formed by any material capable of injecting electron from the cathode, transporting electron or providing barrier against positive holes injected from the anode. Specific examples of such a material include metallic complexes of compounds of the present invention, triazole derivative, oxazole derivative, oxadiazole derivative, fluorenone derivative, anthraquinone dimethane derivative, anthrone derivative, diphenylquinone derivative, thiopyran dioxide derivative, carbodimide derivative, fluorenilidenemethane derivative, distyrylpyrazine derivative, heterocylic tetracarboxylic anhydride such as naphthaleneperylene and phthalocyanine derivative, and metallic complexes having as ligands metal phthalocyanine, benzoxazole or benzothiazole. The thickness of the electron-injecting layer and electron-transporting layer is not specifically limited. In practice, however, it is preferably from 1 nm to 5 xcexcm, more preferably from 5 nm to 1 xcexcm, even more preferably from 10 nm to 500 nm. The electron-injecting layer and electron-transporting layer may have either a single-layer structure comprising one or more of the foregoing materials or a multi-layer structure comprising a plurality of layers having the same or different compositions.
The formation of the electron-injecting layer and electron-transporting layer can be accomplished by vacuum evaporation method, ink jet method, LB method, method involving the application of a dispersion of the foregoing electron-injecting and transporting material (spin coating method, casting method, dip coating method, etc.), or the like may be employed. If coating method is used, these materials may be dissolved or dispersed with a resin component. As such a resin component there may be used those exemplified with reference. to the positive hole-injecting and transporting layers.
The protective layer may be formed by any material capable of preventing the device from being contaminated by materials which accelerate the deterioration of the device such as water content and oxygen. Specific examples of such a material include-metal such as In, Sn, Pb, Au, Cu, Ag, Ti and Ni, metal oxide such as MgO, SiO, SiO2, Al2O3, GeO, NiO, CaO, BaO, Fe2O3, Y2O3 and TiO2, metal fluoride such as MgF2, LiF, AlF3 and CaF2, polyethylene, polypropylene, polymethylene methacrylate, polyimide, polyurea, polytetrafluoroethylene, polychlorotrifluoroethylene, polydichlorodifluoroethylene, copolymer of chlorotrifluoroethylene with dichlorodifluoroethylene, copolymer obtained by the copolymerization of a monomer mixture containing tetrafluoroethylene and at least one comonomer, fluorine-containing copolymer having a cyclic structure in its main chain, hygroscopic material having a percent water absorption of not less than 1%, and moisture proof material having a percent water absorption of not more than 0.1%.
The method for the formation of the protective layer is not specifically limited. For example, vacuum evaporation method, sputtering method, reactive sputtering method, MBE (molecular beam epitaxy) method, cluster ion beam method, ion plating method, plasma polymerization method (high frequency-excited ion plating method), plasma CVD method, laser CVD method, thermal CVD method, gas source CVD method, coating method, etc. may be used.